INTERNAL ANATOMY OF INSECTS. 65 



the scalpel of a Lyonet and the most powerful lenses 

 are adequate to trace the extremities of these vessels ; 

 and even with every help, they at last become so incon- 

 ceivably slender as to elude the most piercing sight. 

 That illustrious anatomist found that the two tracheae of 

 the larva of the Cossus gave birth to 236 bronchial tubes, 

 and that these ramify into no less than 1336 smaller tubes, 

 to which, if 232, the number of the detached bronchiae, 

 be added, the whole will amount to 1804 branches a . 

 Surprising as this number may appear, it is not greater 

 than we may readily conceive to be necessary for com- 

 municating with so many different parts. For, like the 

 arterial and venous trees, which convey and return the 

 blood to and from every part of the body in vertebrate 

 animals, the bronchice are not only carried along the in- 

 testines and spinal marrow, each ganglion of which they 

 penetrate and fill, but they are distributed also to the 

 skin and every organ of the body, entering and travers- 

 ing the legs and wings, the eyes, antennae, and palpi, and 

 accompanying the most minute nerves through their 

 whole course b . How essential to the existence of the 

 animal must the element be that is thus anxiously con- 

 veyed by a thousand channels, so exquisitely formed, to 

 every minute part and portion of it ! Upon considering 

 this wonderful apparatus we may well exclaim, This hath 

 GOD Brought, and this is the work of his hands. 



Though in general there is only SL pair of trachea, yet 

 in some larvae a ""larger number have been discovered. 



a Lyonet 411. b Professor Kidd (Philos. Trans. 



1825. 235.) conjectures that the tracheae, as well as air-vessels, may 

 possibly be blood-vessels ; but this hypothesis is inconsistent with the 

 fact recently discovered by Dr. Cams, of a circulation, by other 

 means, in larva?. See Carus Introd. to Comp. Anat, c. ii. 400, 



VOL. [V. F 



